4 BULLETIN 842, XJ. S. DEPARTMENT OF AGRICULTURE. 



of the disease, and lias pointed out control measures. Later, Cole- 

 man and Regan (10) contributed to our knowledge of the dis- 

 ease so far as it affects the marketing and milling of wheat. A simi- 

 lar disease of several other grasses, thought to be due to a closely 

 related or- identical species of nematode, was reported by Bessey 

 (4) in 1905 and later by the writer, but recent investigations in- 

 dicate that the organisms producing the malady in wheat and other 

 grasses differ physiologically, if not morphologically. The writer's 

 acquaintance with the disease on wheat began in 1915, when minor 

 inoculation experiments were conducted in the greenhouse with 

 material received from China. Interest was renewed during the 

 winter of 1917-18 as the result of finding, in cooperation with the 

 Office of Grain Standardization, an abundance of material in the 

 United States. Consequently, previous experiments in the green- 

 house were repeated and extended, laboratory investigations carried 

 out, and field observations made. These studies are being continued. 



DISTRIBUTION. 



The nematode disease of wheat is of almost world-wide distri- 

 bution, having been reported from all continents except Africa. 

 Sorouer (33), in 1913, stated that it had been found in France, Ger- 

 many, Austria, Hungary, Switzerland, Italy, Sweden, Holland, Eng- 

 land, and North America. Dr. N. A. Cobb 1 has found it many times 

 in Australia and the writer (6) in 1917 reported its occurrence in 

 China. Through the courtesy of Dr. C. E. Leighty, of the Office of 

 Cereal Investigations, Bureau of Plant Industry, an examination of 

 all samples of wheat imported by the United States Department of 

 Agriculture for the past 25 years or more was made and, besides find- 

 ing the disease in material obtained from some of the countries 

 listed above, it was also found in importations originating in Russia, 

 Turkestan, and India, from which places no reference to its occur- 

 rence has been seen. Averna-Sacca (1) in 1912 stated that it occurs 

 in Brazil. From the foregoing account it is evident that the disease 

 can exist under very different climatic and soil conditions and that 

 it is at present of extremely wide occurrence. 



Indications are that the disease has been introduced into this coun- 

 try. That it may be endemic in Europe is suggested by the fact that 

 it was not reported elsewhere for nearly a' century after its dis- 

 covery there. It seems likely that it was first introduced into this 

 ■country with importations of seed wheat from England or continen- 

 tal Europe. The exact native, habitat of the disease, however, is an 

 interesting and open question which may never be definitely an- 



1 In conversation with the writer. Dr. Cobb stated that he had found the trouble on 

 wheat in Australia in 1S92. 



